PDCD1LG2 and breast cancer: Various studies have reported that PD-1, PD-L1, and PD-L2 expression were associated with longer recurrence-free survival, longer disease-specific survival, longer OS, DFS, and PFS in breast cancer (Ali et al., 2015; Baptista et al., 2015; Sabatier et al., 2015.; Schalper et al., 2014; Uhercik et al., 2017; Yearley et al., 2017).